Aqua-Tru liners are sealed using Therma-Seal Technology which is a proprietary fusion method providing superior sealing for maximum durability and quality. The UD (Uniform Depth) Liners - Heavy Duty Solid Blue Liner series has Ultraviolet Inhibitors that protect the liner from the sun's rays and enhance longer life. It is specially designed to be wrinkle-free when used for those economical, kick-in installations. All its sidewalls and bottoms are manufactured to the same thickness and weight. It is remarkably manufactured to a "Tru" mil thickness. This particular product, 8' Heavy Duty Solid Blue Round UD Pool Liner, is 8 feet in size with a Solid Blue overlap liner patterns and this product is fit for Round Above Ground Pools.